Methods and means for monitoring eccentricities of coaxial members

ABSTRACT

As welding electrodes are mass-produced, the mean eccentricity of a number of the electrodes&#39;&#39; wires with respect to their surrounding sheaths is monitored, by sequentially passing parallel ones of the electrodes radially past an X-ray source. For each electrode a comparison is made of the X-ray radiation absorbed by the sheath on one side of the wire with that on the other side of the wire. The absorption measurements indicate when the sheath begins to pass the source, when the rod begins to pass the source, when the rod stops passing the source, and when the sheath stops passing the source. The absolute values of the comparisons are totaled to obtain an indication of the average eccentricity.

United States Patent [1 1 [111 3,770,959

Gloor et al. [4 1 Nov. 6, 1973 [54] METHODS AND MEANS FOR MONITORING3,6l 1,408 /1971 Shoemaker et al 250/833 D X ECCENTRICITIES OF COMEMBERS 3,654,468 4/1972 Shah 250/833 D X [75] Inventors: Karl Gloor,Zollikon; Eugen Halter, v

Zuerich, both of Switzerland 52 figgi g q g zj' Bo'rchelt 0rney c e y[73] Assignee: Schweissindustrie Oerlikon Buhrle AG, Zuerich,Switzerland [57] ABSTRACT [22] Filed: June 3, 1971 As welding electrodesare mass-produced, the mean ec- PP 149,759 centricity of a number of theelectrodes wires with respect to their surrounding sheaths is monitored,by se- [30] Foreign Application Priority Data qllientially pissingparalleLones ohii" tll'ie telegtrodes radia y pas an -ray source. or eace ec ro e acompar- June 4, 1970 Switzerland 8400/70 ison is made of they radiation absorbed y the sheath on one side of the wire with that onthe other 'r side of the wire. The abso ption measurements indicate whenthe sheath begins to pass the source, when the [58] Field of Search250/83.3 D

rod begins to pass the source,twhen the rod stops pass- [5 6] ReferencesCited mg the source, and when the sheath stops passing the source. Theabsolute values of the comparisons are to- UNITED STATES PATENTS taledto obtain an indication of the average eccentric- 3,148,279 9/1964 Skala250/833 D ity 3,390,769 7/1968 Tatham et al... 250/833 D X 3,609,3689/l97l Knorr et al. 250/833 D X 33 Claims, 4 Drawing FiguresMANUFACTURING g SOJ APPARATUS 51 O O PRESELECTOFi-36 COM PA RATORIOMZATION 24 Q t AND CONTROL-35 c H AM BE R 25 COM PARATOR- 28 DC AMP.-27

PULSE om- 26 2 COUNTER-30] COUNTER-32 S ORAGE-37 Ao R i T RA DE 33 7 s 0GE 38 iNDlCATOR-40 COMPARATOR 31 INDICATOR-4i woman-34,

BACKGROUND OF THE INVENTION This invention relates to mass production ofdevices including coaxial portions and the monitoring of theireccentricities, and particularly to the monitoring of the eccentricitiesof electric welding rods or electrodes composed of a central metallicwelding wire which is surrounded by a welding powder sheath that is ascoaxial as possible relative to the wire.

Such electric welding electrodes are usually produced in largequantities, such as 1901) electrodes/min with cylindrical metallicwelding wires and surrounding powder sheaths. The electrodes producedare generally moved on a high speed conveyor belt where they are alignedsubstantially parallel with each other and transverse to the directionof movement of the belt.

Becauseof the manufacturing methods used, the individual electrodesusually exhibit a certain amount of eccentricity E. That is to say thewelding wire and the welding powder sheath are not always exactlycoaxial relative to each other but are eccentric. The eccentricity E,which is a measure for the deviation from the coaxial condition isdefined as the distance of the radial centers of the two cylindersformed by the welding wire and the welding powder sheath.

The radial direction of the individual eccentricities of the electrodesor rods as they are moved onto the moving belt is evenly distributedwhen considered on a statistical basis. The maximum eccentricitytolerated in the manufacture should not be exceeded, if possible.Otherwise the quality of the electrodes will suffer.

in order to supervise the machine and the production apparatus, thestatistically average eccentricity of the welding electrodes should betested non-destructively.

Another object of the invention is to improve such measuring systems.

SUMMARY OF THE INVENTION According to a feature of the invention, theseobjects are attained and the disadvantages obviated by sequentiallymoving individual rods in a direction having a radial component past anenergy source that penetrates the sheaths differently than the wires,and,after sensing the energy penetrating the sheath on the leadingradial side of the wire and then subtracting the radiation passingthrough the trailing side of each rod so as to achieve a comparison foreach rod, adding the absolute values of the comparisons for apredetermined number of rods.

According to another feature of the invention, the number of rods arecounted and the addition stopped after the predetermined number of rods.

According to still another feature of the invention, the amount ofpenetration is measured by obtaining an indication of the distance overwhich the sensor senses penetration through the sheath on the leadingradial side of the wire and on the trailing radial side of the wire.

According to yet another feature of the invention, the penetration ismeasured by establishing thresholds of penetration separating thepenetration of the sheaths and the wires.

According to still another feature of the invention, the energy sourceis composed of an X-ray and the penetration is measured by an ionizationchamber that measures the absorptions of the sheaths and the wires.

This would allow the production of a more satisfactory product.

ln the past, a statistical random test was used. A test electrode or rodwas removed by hand from the electrodes on the moving belt at regularintervals. The azimuthal variation of the eccentricity was determinedby, the variations in the permeability exhibited by the electrodes in aconstant stationary magnetic field. This variation was noted by turningthe electrode by hand about its longitudinal axis. This method was usedto determine whether the eccentricity was within a desired range oftolerance.

This method of testing andmeasuring the statistical mean value of theeccentricity of the electrodes has a number of shortcomings. Forexample, .it can only be used with welding rods utilizing ferromagneticmaterial. For example, it could not be used with welding rods usingaluminum wires. The method of testing a random sample was somewhatsubjective. This resulted in systematic subjective averaging errors.When this system is used with great production numbers, the intervalbetween the random tests with a fixed number of testers becomes toogreat. That is to say, the results be- .come less accurate with a largenumber of rods. On the other hand, to achieve constantly accurateresults requires a great number of testers. It becomes too expensive.Moreover, this manual random sampling and.test-,

ing cannot be automated and is thus uneconomical.

An object of the present invention is to eliminate the above-describeddisadvantages.

According to still another feature of the invention, a first thresholdis established to indicate that the absorption exceeds the absorption ofthe medium surrounding the rods to thereby denote that the sheath isabsorbing the X-ray radiation, and a second higher absorption thresholdis established to indicate that the wire is passing under the source andabsorbing the radiation.

According to still another feature of the invention, the distance overwhich the ionization chamber measures the absorption of the sheaths asthe rods pass the source, is determined by a counter that counts pulseswhose rate depends upon the speed at which the belt moves the rods pastthe source.

I According to yet another featureof the invention, the counter countsup for pulses that occur during passage of the leading radial side ofthe sheath and counts down for pulses which occur as the trailing radialside of the sheath passes the source.

According to'another featureof the invention, an

adding device adds the absolute value of each rods net number of pulsesand after a predetermined number of rods have beenmeasured, the totalis'displayed and erased for a new count.

Because of these features, all types of welding electrodes whose weldingwires and welding powder sheaths permit different penetrations orexhibit different absorption capacities for X-rays,or other types ofonly those using ferromagnetic welding wires. The invention minimizessubjective measuring errors that occur as a result of manual random:testing. The invention carries out the monitoring automatically and canbe used without additional personnel. The mean eccentricity can beascertained over any selected number of electrodes. Likewise, thevelocity of the feed of the electrodes can be selected at random.

Furthermore the measuring values are determined, according to thefeatures of the invention, while the welding electrodes move on a belt.The method according to the invention is therefore suitable for use withsystems producing large or small numbers of electrodes. The inventionyields mean values which are independent of the number.

An advantage of the method according to the invention is that the numberof electrodes not used for ascertaining the mean value can be countedautomatically. In addition, the thickness of the sheath can besupervised by additional means. This is important in order to replacethe sheathing nozzle when it is worn out, as may be required foreconomic or technical reasons.

These and other features of the invention are pointed out in the claimsforming a part of this specification. Other objects and advantages ofthe invention will become known from the following detailed descriptionwhen read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially schematic andpartially block diagram of a welding rod eccentricity monitoring systemembodying features of the invention;

FIG. 2 is a schematic illustration showing electrodes carried by aconveyor belt and indicating different azimuthal positions or radialdirections of eccentricities in the respective rods;

FIG. 3' is a schematic diagram illustrating the crosssection through awelding electrode and showing an example of the eccentricity of the wirewithin the electrode; and

FIG. 4 is a current-time diagram illustrating the absorption experiencedby radiation as an electrode, such as the one of FIG. 3 passes a sourceof radiation.

DESCRIPTION OF PREFERRED EMBODIMENTS In FIG. 1 a continuously movingendless belt 18 carries a number of welding electrodes 22 emerging froma manufacturing apparatus 50, in the direction indicated by the arrow51. The belt 18 carries each of the electrodes which extend transverseto the direction of the movement of the belt 18 past a direct currentX-ray source 21. The latter has a narrow focal point for producing anarrow cone of X-rays 23. The source has substantial power so as toproduce largely intensive rays. In the embodiment illustrated in FIG. 1,the focal point has an extension of less than 0.25 mm with an electroncurrent of 2.5mA and a tube voltage of IOOkV. The cone of rays 23 arediaphragmed narrowly enough so as to pass perpendicularly relative tothe electrodes 22 on the conveyor belt 18. The electrodes 22 extendparallel to each other, and as stated, transverse to the direction ofthe feed of the belt.

An ionization chamber 24 which is filled with air or xenon generates anionic current I which corresponds,

at any moment to the intensity of the radiation passing through adiaphragm 24 in the ionization chamber. A

direct-current amplifier 27 amplifies the current I.

tion of the motion of the belt is from right to left, as indicated bythe arrow. The electrodes extend transverse to the direction of themovement of the belt 18, and are substantially parallel to each other.They come directly from the manufacturing apparatus 50 and can,accidentally, touch each other depending upon the ejection rate.Alignment means 52, which are also illustrated in FIG. 1, align theelectrodes parallel to each other before they pass the source 21.

FIG. 3 illustrates a detailed cross-section of one of these electrodes.Here a cylindrical outer sheath OS surrounds a cylindrical wire W. Theouter sheath is composed of a powder material which is sintered orotherwise caked onto the wire W. The electrode 22 exhibits aneccentricity E. The latter represents the shift of the center B of thewire W from the center A of the outer sheath OS. Thus the eccentricity Ereally represents the eccentricity of the wire W within the sheath OS.

The eccentricity E is a substantially unavoidable effect. The desiredresult from production is an absence of eccentricity, that is an outersheath OS coaxially surrounding the wire W. Under those circumstancesthe center A coincides with the center B. However, be-

cause of manufacturing tolerances, electrodes 22 usually exhibit theeccentricity illustrated in FIG. 3. In a manufacturing apparatus, suchas the apparatus 50, the magnitudes of the eccentricities of largenumbers of electrodes follow a substantially Gaussian distribution abouta specific mean value with a given variance.

Because of the manner in which the electrodes are ejected from themanufacturing apparatus 50, the radial directions of the eccentricitiesare distributed almost evenly on a statistical basis, as indicated bytests. FIG. 2 illustrates a number of directions that the eccentricitiesmight exhibit as they are ejected from the manufacturing apparatus 50.In FIG. 2, the open circles 55 illustrate the sample directions of theeccentricities in the electrodes 11 17 with respect to the centers ofthese electrodes, while the darkened spots 56 indicate the tops of theelectrodes. Thus, the darkened spots represent the intersection of avertical line C through the center of an electrode with the outerperiphery of the sheath OS. In the electrode 11 the direction of theeccentricity is explicitly indicated by a straight line F through thecenter of the electrode 11 and the small circle 55. The line Cillustrates the fixed vertical direction of the cone of X-rays. Asclearly seen with respect to electrode 11, the relative position of theaccidental eccentricity directions to the fixed directions of theradiation of the cone of X-rays is indicated by the angle 1). It followsthat the angle (1: is evenly distributed statistically.

Thus, as the electrodes 22 pass the cone 23 from the source 21, theeccentricity can extend in anyone of a number of directions. The effectof extending in one direction or another has a considerable effect uponthe measurement. Thus, for example, as an electrode, such as the oneshown in FIG. 3, passes through the cone 23, the ionization chamber 25first responds to the penetration of the portion a of the outer sheathOS. The current produced by the ionization chamber would thus follow thepath indicated by the absorption curve in FIG. 4. Initially, just beforethe electrode enters the range of the cone 23, the current I produced bythe ionization chamber is quite high and indicative of substan tially noabsorption. As the electrode enters the cone 23 the sheath OS begins toabsorb some of the energy in the portion a. This absorption increases sothat the current I produced by the ionization chamber 25 decreases. Whenthe core wire W first enters the narrow cone at the time T the current Isuddenly decreases 5 below a value I This is indicative of the suddenjump in absorption by the core wire W. At the time T when the core wireemerges from the narrow cone 23, the current I jumps rapidly back to ahigher value indicating that only the sheath is absorbing energy. Thisoccurs in the portion of the sheath b of FIG. 3. When the rod emergesfrom the cone 23 entirely, the current I from the chamber 25 again jumpsto the zero absorption value Since the absorption rate as the electrodeenters the cone 23 does not drop discontinuously, a value I is chosenbeyond which or below which the sheath is presumed to have entered thecone at the time T and above which the sheath is presumed to have leftthe cone 23 at the time T The value I is selected to coincide withapproximately the center of the discontinuities occurring as the wire Wenters and leaves the cone 23. These discontinuties occur at times T andT The measurement of time from T to T and T to T. produces two values,a,, and b',,,, which are approximately equalto a and b. As can be seenfrom FIG. 3, when the eccentricity is oriented in the direction shown,the eccentricity of the electrode is given by Thus an indication of(a',, b',,,)/2 constitutesa substantial approximation of theeccentricity E. However, it can be seen that if the electrode is rotatedand the cone radiates energy from the direction D as shown in FIG. 3,values a and b' are obtained from the absorp- 3 tion measurements. Thedirection D, however, forms an angle 2. 1b with the eccentricity. Forthis reason, an absorption measurement crresponding to (a',,, b',,,)/2does not yield a value corresponding to the eccentricity E. Rather ityields the projection E in the direction D. 4

We thus have E (a b')/2 =E sin (1).

the statistical mean value of the various projectedeccentricities with acontinuous angle (b is obtained by the integration of the equation (2)for E over the angle 4: in an interval from 0 to 11/2 with thestatistical weight 1/ (qr/2 Thus, if a bracket characterizes theapproximation to the mean, we have Thus the eccentricity E of anelectrode has the value This continuous averaging can be-meaningful only65 for a large number of electrodes and a large number of directionsThus, the validity of the measuring method is ensured by satisfyingthese conditions.

Combining the equation (2) with equation (5) produces Continuousaveraging according to the equation (3) analogously yields The meaneccentricity follows from equation (5) which yields Equation (8) is thebasis for the new method.

FIG. 4 specifically shows the absorption curve for the m-th measurementproduced by the ionic current in the ionization chamber 25. The ioniccurrent I generated in the ionization chamber corresponds to theintensity variation of the X-rays traversing the-electrode as am plifiedwith the d-c amplifier 27. This current [when applied to a measuringrecorder 29, yields the curve illustrated in FIG. 4 as a function oftime T.

Inthe curve of FIG. 4 we can clearly see three regions, I, II and Ill.The two outer regions I and III, which determine the sections a',, andb',, correspond to the absorption by the welding powder sheath,and theinnerregion II corresponds to that of the core wire W. The substantialdiscontinuities of the absorption at the start and at the end of thecore wire regions have great importance. Similar discontinuities at thestart and at the end of the electrodes themselves, that is at the edgesof the electrodes, are also important. The jumps of the absorptioncurves at these discontinuity points all occur over a practically zerotime. For this reason, the value of the ionic currents I and I canreadily be obtained from the absorption curves at the discontinuitypoints. In this way the start and] the ends of the various regions canbe defined.

Since the current value rises almost vertically in the proximity of thediscontinuity points for the absorption curve, the determination ofthreshold values is not critical. That is fluctuations about a meanvalue of the order of up to percent have no influence on the result ofthe measurements. According to one embodiment of the invention the mostfavorable threshold values l, and I are determined for specificelectrodes from a number of absorption curves in the measuring recorder29. This then is used to adjust the comparator 28 at the terminals 43and 44 to obtain automatic measurements of the mean eccentricity.

According to one embodiment of the invention, the X-ray source 21 andthe ionization chamber 25 retain a fixed position. According to anotherembodiment of the invention, a measuring table (not shown) continuouslydisplaces the X-ray source and the ionization chamber, which togetherform a measuring head, parallel to the electrode axes. Consequently,each measurement determines not only the eccentricity through onesection of the electrodes but determines the average eccentricity ofeach electrode over its entire length.

As stated, the d-c amplifier 27 applies its output to a measuringrecorder so the absorption curves corresponding to FIG. 4 are recorded.A determination is then made of the threshold values I, and I suitablefor the particular type of electrodes being manufactured by theapparatus 50. Once the threshold values have been determined, they areadjusted on the'input 43 and 44 of comparator 28. The comparator 28determines the times T, to T,, as shown in FIG. 4, at which theamplified ionic current I passes through the preset current levels I,and 1 During the intervals T, to T the comparator 28 releases oractuates the up-count or forward-count of an up-down counter, orforwardbackward counter 30. During the interval between time T to T, thecomparator 28 actuates the up-down counter 30 to count down. Thecounting direction is determined by the chronological order of the levelI, and That is to say, when the order of currents is l, to 1,, thecounter 30 counts up while for the inverted order 1 1, causes thecounter 30 to count down. When the ionic current thus drops below thelevel 1,, the counter 30 counts up. When the ionic current passes upthrough the current level 1 the counter 30 counts down.

A pulse generator 26 whose rate responds to the speed of the conveyorbelt 18 serves as the pulse frequency timer for the counter 30. Thus, nomatter what the belt speed that is used, the operation of the counter 30corresponds to that speed. Thus, fluctuations in the belt speed do notaffect operation of the apparatus according to the invention.

The counter 30 thus substantially subtracts the number of pulses duringthe time interval T to T from the time interval T, to T At the time T,the counter 30 thus indicates the difference in the number of pulsescounted during these two intervals. This difference is proportional tothe mass difference indicated by the equation (2). The counter 30produces an output cor responding only to the absolute value of thedifference. This prevents electrodes which have eccentricities extendingin one direction from cancelling out the effects electrodes havingeccentricities extending in the other direction. In fact it prevents thetotal result of all the measurements of the electrodes from becomingvirtually zero. The counter accomplishes this absolute value output witha known logical decision element that reverses the measuring resultafter each electrode if the time between T and T is greater than thetime between T, and T The comparator 31 compares the eccentricitydetermined for each electrode with a maximum admissible eccentricityentered at point 44 of this comparator. The comparator 31 excludesindividual extreme eccentricities and passes the net eccentricity pulsesfrom the counter 30, with the exception of those excluded, to an adder33. The latter adds the eccentricity of the last electrode 22 whosemeasurement has not been rejected by the comparator 31, to those ofprevious eccentricities and stores the total in a storage device 38. Anindicator 41 displays the content of the storage device 38.

It should be noted here that the counter is reset to zero aftermeasuring each electrode. (Counter 30).

A counter 34 counts the number of electrodes whose measurements wererejected by the comparator 31 so as not to be used in determining themean value. It also counts the value of the eccentricities beingrejected and stores both figures in a storage device 39 whose content isdisplayed by an indicator 42. The extreme measurements rejected by thecomparator 31 can arise from poorly manufactured electrodes,disturbances due to electrical interference pulses, or mechanicallydamaged electrodes. According to one embodiment of the invention, thecounter 34 records a maximum number of nine electrodes. The eliminationlimit is 39,

pulses which would correspond to an eccentricity of about 0.39 mm.

A counter 32 counts all the measured electrodes and stores them in astorage device 37. At the same time a comparator and. control unit 35compares the number of electrodes counted in the counter 32 with apreselected number N established by a preselector 36. The unit 35actuates the storage devices 37, 38 and 39 to transfer their content tothe indicators 40, 41 and 42 when the number N has been reached by thecounter 32. Thus display by the indicators 40, 41 and 42 occurs onlywhen the storages 37, 38 and 39 have reached their limit as determinedby the control unit 35. The number of excluded electrodes is thusdisplayed in the indicator 42. The end sum of the errors of the averagedeccentricities is displayed in the indicator 41. The indicator 40displays the total number N of the measured electrodes.

With a slight delay the adding device 37 and the counters 32 and 34 arethen erased to be ready for the measurement of the next N number ofelectrodes. The content of the storage units 37, 38 and 39 are reset toaccept the new values from the counter 32, adder 33 and counter 34. Themeasuring data are indicated during the entire measuring time of thenext N electrodes. That is, ifN 100, a time of 2 to 3 seconds isavailable.

According to one embodiment of the invention, the indicators 40, 41 and42 are composed of decoding units and digital indicating tubes. Themeasuring values can be used for additional statistical evaluation, likedetermination of the variance and averaging over far greater numbers.

According to another embodiment of the invention, the value indicated bythe indicator 41 is transmitted electrically to the manufacturingapparatus 50 so as to adjust the apparatus and cause it to produceelectrodes within closer tolerances where necessary. The values inindicators 40 and 42 are also transmitted to the appara- I tus 50 wherethey are combined with the value in indicator 40 to aid in theadjustment.

Apart from the do amplifier 27, the entire electronic evaluation systemis composed of integrated circuit parts. The ionization chamber 25 isconstructed specially with small electrode plate spacings so as toproduce usable analog signals. The arrangement is thus very sensitive tomechanical vibrations of the electrode plates. Special mounts eliminatevibrations that may be transmitted from the belt to the ionizationchamber. The amplifier 27 is a d-c amplifier with a field-effecttransistor at the input stage.

According to one embodiment of the invention, the measuring recorder 29is composed of a counter having a logic circuit ratherthan a display.These determine the intervals T, to T, and T to T The thresholds arethen set at the optimum values when each interval T to T are determined.The-thresholds are set at the optimum values when the interval T to Tcorresponds to the wire diameter and the interval T, to T to the widthof the diameter of the electrode reduced by'the cone 23 of rays.

While embodiments of the invention has been described in detail, it willbe obvious that the invention may be embodied otherwise withoutdeparting from its spirit.

What is climaed is: t

l. The method of observing eccentricities of interior members relativeto surrounding sheaths where said mem hers and sheaths form assemblies,which comprises moving the assemblies sequentially through a beamemanating from an energy source and exhibiting different amounts ofpenetration through the members relative to the sheaths, for eachassembly measuring the distance over which a sensor senses penetration asecond higher} absorption threshold is established to indicate that theinterior member is passing under the source and absorbing the energy.

8. The method as in claim 1, wherein the assemblies are composed ofwelding rods and the central members are composed of welding wires.

9. The method as in claim 1, wherein aftereach comparison of themeasurements of the penetration of the leading edge and the trailingedge the measurements are erased.

10. The method as in claim 2, wherein after the assemblies are countedand the comparisons stopped after a predetermined number of assembliesthe addition is erased.

11. The method asin claim 1, wherein the assemblies are moved with aselectable feed velocity.

12. The'method as in claim 1, wherein the rods are arrayed parallel toeach other and moved transverse to their longitudinal direction andtransverse to the direction of the beam.

13. The method as in claim 1, further comprising comparing eachcomparison with a standard maximum value and eliminating measurementsexceeding the rior members relative to sheaths, wherein the interiorthrough the sheath from the edge of the sheath to the member on theleading radial side of the member as the leading radial side of thesheath passesthrough the beam, for each assembly measuring the distanceover which a sensor senses penetration through the sheath from themember to the edge of the sheath on the trailing radial side of thesheath as it passes through the beam, comparing the measurements on eachradial side of the member, and comparisons. the absolute values of thecimparisons.

2. The method as in claim 1, further comprising counting the number ofassemblies and stopping the comparisonafter a predetermined number ofassem-. blies.

3. The method asin claim 1, wherein the amounts of penetration aremeasured by obtaining measures of the distance over which a sensorsenses penetration.

through the sheath on the leading radial side of the interior member andon the trailing radial side of the interior member. t

4. The method as in claim 3, wherein the distances are measured'bycounting time intervals whose length is based on the speed at which the,assemblies are moved through the beam.

5. The method as in claim 1, wherein the distances are measured byestablishing thresholds of penetration separating the penetration of thesheaths and the interior members.

6. The method as in claim 1, wherein the energy source is an X-ray, andwherein the penetration is measured by an ionization chamber thatmeasures the absorption of the X rays by the portions of the assemblies.

7. The method as in claim 6, wherein a first threshold is established toindicate that the absorption exceeds the medium surrounding theassemblies to thereby denote that the sheath is absorbing X-rayradiation, and

members and sheaths form assemblies, comprising energy source means forforming a beamexhibiting different amounts of penetration through themember relative to the sheath, moving means'for moving the beam and aplurality'of the assemblies relative to each other so as to pass theassemblies through the beam, sensing means in the path of the beam forsensing when the beam is passing through the sheath on the leading andthen the trailing side of the member, measuring means connected to saidsensing means for comparing the dis tance over which said sensor meanssenses penetration through the sheath on the leading radial side of themember from the edge of the sheath to the member with the distance overwhich said sensor means senses penetration through the sheath onthetrailing side of the member from the member to the edge of the sheath,and adding means connected to said measuring means for adding theabsolute values of the comparedmeasurements. l

15. An apparatus'as in claim 14, wherein the assemblies are elongatedwelding rods and the interior members are wires,and wherein said movingmeans move the rods so they exhibit a moving radial component relativeto the beam.

16. An apparatus as in claim 15, wherein said moving means includes abelt carryingv the rods transverse to the'direction of motion.

17. An apparatus as in claim 16, wherein said measuring means includespulse generator measn responsive to the speed of said belt forproducingpulses and an up-down counter for counting up during the pulses whentheir leading radial side of each sheath passesthrough the beam andcounting down when the trailing radial side of the sheath passes throughthe beam, and conversion means in said up-down counter for producing avalue indicative of the absolute value in the counter after eachmeasurement of both radial sides of the sheath.

18. An apparatus as in claim 14, wherein said measuring means includeserase means for erasing each measurement after each sensing of eachassembly.

19. An apparatus as in claim 17, wherein said measuring means includeserase means for erasing each absolute value after said adding means hasadded the absolute values.

20. An apparatus as in claim 19, wherein said measuring means includespreselector means connected to said counter and said adding means forcounting the number of rods passing through the beam and comparing themwith a given number and then stopping the addition in said adding meanswhen the given number is exceeded.

21. An apparatus as in claim 20, wherein said adding means includes anadder, storage means for storing the added values and ending addition inresponse to said preselector means, and indicator'means.

22. An apparatus as in claim 14, wherein said sensing means includethreshold forming means for establishing thresholds indicative of sensedvalues corresponding to the sheath entering the beam, the memberentering the beam, the member leaving the beam, and the sheath leavingthe beam; and wherein said measuring means measures the penetration timefrom the threshold occurring when the sheath enters the beam to the timewhen the member enters the beam, and compares it with the time from thethreshold at which the member leaves the beam and the sheath leaves thebeam.

23. An apparatus as in claim 14, wherein said source means includes anX-ray machine, and wherein said sensing means includes an ionizationchamber.

24. An apparatus as in claim 23, wherein the beam is such as topenetrate the sheath and the member so as to form step functions at theoutput of said measuring means as the sheath enters the beam, as themember enters the beam, as the member leaves the beam and as the sheathleaves the beam, and wherein the thresholds are selected at the stepfunctions.

25. An apparatus as in claim 24, wherein logic means measure the stepfunctions.

26. An apparatus as in claim 14, wherein said measuring means includescomparator means for comparing the individual absolute values with agiven maximum value and for shunting values in excess of the maximumvalues away from the adding means so that the excessive values are notadded.

27. An apparatus as in claim 14, wherein said sensing means includes anionization chamber, said ionization chamber including mounting means forabsorbing vibrations.

28. A method as in claim 1, wherein the beam has an effective diameterless than the distances to be measured.

29. A method as in claim 7, wherein the beam has an effective diameterless than the distances to be measured.

30. An apparatus as in claim 14, wherein said energy source meansproduces the beam so its diameter is less than the distances to bemeasured.

31. An apparatus as in claim 24, wherein said energy source meansproduces the beam so its diameter is less than the distances to bemeasured.

32. A method as in claim v1, wherein the beam exhib-.

its one range of penetration through the sheaths and a second rangethrough the members.

33. An apparatus as in claim 14, wherein said energy source means formsa beam that exhibits one range of penetration through the sheaths andanother range of penetration through the members.

1. The method of observing eccentricities of interior members relativeto surrounding sheaths where said members and sheaths form assemblies,which comprises moving the assemblies sequentially through a beamemanating from an energy source and exhibiting different amounts ofpenetration through the members relative to the sheaths, for eachassembly measuring the distance over which a sensor senses penetrationthrough the sheath from the edge of the sheath to the member on theleading radial side of the member as the leading radial side of thesheath passes through the beam, for each assembly measuring the distanceover which a sensor senses penetration through the sheath from themember to the edge of the sheath on the trailing radial side of thesheath as it passes through the beam, comparing the measurements on eachradial side of the member, and comparisons. the absolute values of thecimparisons.
 2. The method as in claim 1, further comprising countingthe number of assemblies and stopping the comparison after apredetermined number of assemblies.
 3. The method as in claim 1, whereinthe amounts of penetration are measured by obtaining measures of thedistance over which a sensor senses penetration through the sheath onthe leading radial side of the interior member and on the trailingradial side of the interior member.
 4. The method as in claim 3, whereinthe distances are measured by counting time intervals whose length isbased on the speed at which the assemblies are moved through the beam.5. The method as in claim 1, wherein the distances are measured byestablishing thresholds of penetration separating the penetration of thesheaths and the interior members.
 6. The method as in claim 1, whereinthe energy source is an X-ray, and wherein the penetration is measuredby an ionization chamber that measures the absorption of the X-rays bythe portions of the assemblies.
 7. The method as in claim 6, wherein afirst threshold is established to indicate that the absorption exceedsthe medium surrounding the assemblies to thereby denote that the sheathis absorbing X-ray radiation, and a second higher absorption thresholdis established to indicate that the interior member is passing under thesource and absorbing the energy.
 8. The method as in claim 1, whereinthe assemblies are composed of welding rods and the central members arecomposed of welding wires.
 9. The method as in claim 1, wherein aftereach comparison of the measurements of the penetration of the leadingedge and the trailing edge the measurements are erased.
 10. The methodas in claim 2, wherein after the assemblies are counted and thecomparisons stopped after a predetermined number of assemblies theaddition is erased.
 11. The method as in claim 1, wherein the assembliesare moved with a selectable feed velocity.
 12. The method as in claim 1,wherein the rods are arrayed parallel to each other and moved transverseto their longitudinal direction and transverse to the direction of thebeam.
 13. The method as in claim 1, further comprising comparing eachcomparison with a standard maximum value and eliminating measurementsexceeding the maximum value so as not to be included in the total of theadding step.
 14. An apparatus for observing eccentricities of interiormembers relative to sheaths, wherein the interior members and sheathsform assemblies, comprising energy source means for forming a beamexhibiting different amounts of penetration through the member relativeto the sheath, moving means for moving the beam and a plurality of theassemblies relative to each other so as to pass the assemblies throughthe beam, sensing means in the path of the beam for sensing when thebeam is passing through the sheath on the leading and then the trailingside of the member, measuring means connected to said sensing means forcomparing the distance over which said sensor means senses penetrationthrough the sheath on the leading radial side of the member from theedge of the sheath to the member with the distance over which saidsensor means senses penetration through the sheath on the trailing sideof the member from the member to the edge of the sheath, and addingmeans connected to said measuring means for adding the absolute valuesof the compared measurements.
 15. An apparatus as in claim 14, whereinthe assemblies are elongated welding rods and the interior members arewires, and wherein said moving means move the rods so they exhibit amoving radial component relative to the beam.
 16. An apparatus as inclaim 15, wherein said moving means includes a belt carrying the rodstransverse to the direction of motion.
 17. An apparatus as in claim 16,wherein said measuring means includes pulse generator measn responsiveto the speed of said belt for producing pulses and an up-down counterfor counting up during the pulses when their leading radial side of eachsheath passes through the beam and counting down when the trailingradial side of the sheath passes through the beam, and conversion meansin said up-down counter for producing a value indicative of the absolutevalue in the counter after each measurement of both radial sides of thesheath.
 18. An apparatus as in claim 14, wherein said measuring meansincludes erase means for erasing each measurement after each sensing ofeach assembly.
 19. An apparatus as in claim 17, wherein said measuringmeans includes erase means for erasing each absolute value after saidadding means has added the absolute values.
 20. An apparatus as in claim19, wherein said measuring means includes preselector means connected tosaid counter and said adding means for counting the number of rodspassing through the beam and comparing them with a given number and thenstopping the addition in said adding means when the given number isexceeded.
 21. An apparatus as in claim 20, wherein said adding meansincludes an adder, storage means for storing the added values and endingaddition in response to said preselector means, and indicator means. 22.An apparatus as in claim 14, wherein said sensing means includethreshold forming means for establishing thresholds indicative of sensedvalues corresponding to the sheath entering the beam, the memberentering the beam, the member leaving the beam, and the sheath leavingthe beam; and wherein said measuring means measures the penetration timefrom the threShold occurring when the sheath enters the beam to the timewhen the member enters the beam, and compares it with the time from thethreshold at which the member leaves the beam and the sheath leaves thebeam.
 23. An apparatus as in claim 14, wherein said source meansincludes an X-ray machine, and wherein said sensing means includes anionization chamber.
 24. An apparatus as in claim 23, wherein the beam issuch as to penetrate the sheath and the member so as to form stepfunctions at the output of said measuring means as the sheath enters thebeam, as the member enters the beam, as the member leaves the beam andas the sheath leaves the beam, and wherein the thresholds are selectedat the step functions.
 25. An apparatus as in claim 24, wherein logicmeans measure the step functions.
 26. An apparatus as in claim 14,wherein said measuring means includes comparator means for comparing theindividual absolute values with a given maximum value and for shuntingvalues in excess of the maximum values away from the adding means sothat the excessive values are not added.
 27. An apparatus as in claim14, wherein said sensing means includes an ionization chamber, saidionization chamber including mounting means for absorbing vibrations.28. A method as in claim 1, wherein the beam has an effective diameterless than the distances to be measured.
 29. A method as in claim 7,wherein the beam has an effective diameter less than the distances to bemeasured.
 30. An apparatus as in claim 14, wherein said energy sourcemeans produces the beam so its diameter is less than the distances to bemeasured.
 31. An apparatus as in claim 24, wherein said energy sourcemeans produces the beam so its diameter is less than the distances to bemeasured.
 32. A method as in claim 1, wherein the beam exhibits onerange of penetration through the sheaths and a second range through themembers.
 33. An apparatus as in claim 14, wherein said energy sourcemeans forms a beam that exhibits one range of penetration through thesheaths and another range of penetration through the members.